Felix Radensky wrote:

Hi, Wolfgang

Wolfgang Grandegger wrote:

quoted

Felix Radensky wrote:
 

quoted

Hi,

Almost all MPC85XX based systems have the compatible=:"fsl-i2c" in
respective
i2c device tree nodes. This causes FSL i2c driver to use the following
"backward
compatible" values: FSR=0x31 DFSR=0x10. This is regardless of CCB clock
frequency and i2c clock prescaler.

On my custom MPC8536 based board with 432MHz CCB clock this results in
65KHz i2c clock frequency (checked with scope). U-Boot correctly
configures
the clock to 400KHz.

I've fixed the problem by modifying device tree to use different
compatible value,
similar to what socrates board does. Is this the right approach ?
    

Are you aware of the properties described in
"Documentation/powerpc/dts-bindings/fsl/i2c.txt":

http://lxr.linux.no/#linux+v2.6.32/Documentation/powerpc/dts-bindings/fsl/i2c.txt


Wolfgang.

  

Sure, I'm aware of these properties. I've used

compatible = "fsl,mpc8543-i2c", "fsl-i2c";
clock-frequency = <400000>;

for my custom board.

I think, however, that device trees for FSL reference designs should use
them as well, to avoid setting i2c
clock to some strange values. I may be wrong, but I think most custom

The FSR=0x31 DFSR=0x10 are not strange values. They have been used in
mainline kernels (< 2.6.30) for a long time.

board developers borrow from
reference device trees, so having a sane starting point would help.

The trees provided by Freescale are usually based on older kernel
version. Borrow from such trees is OK, but the project developers should
use a recent kernel version for development.

Wolfgang.